java中預設的計算是不支援很精確的小數位運算，但是使用bigDecimal類的方法可以解決此問題。

下面是我在專案中封裝的一個工具類。供大家參考

/**
 * 高精度計算工具類
 *
 * @author Leon
 * @version 2018/4/18 11:56
 */
public class ArithmeticUtil {

    /**
     * default divide scale
     */
    private static final int DEFAULT_DIVIDE_SCALE = 10;

    /**
     *default add scale
     */
    private static final int DEFAULT_ADD_SCALE = 4;

    /**
     *default subtract scale
     */
    private static final int DEFAULT_SUB_SCALE = 4;

    /**
     * default multiplicative default
     */
    private static final int DEFAULT_MULTI_SCALE = 10;

    /**
     * default scale
     */
    private static final int DEFAULT_SCALE = 2;

    /**
     * private constructor
     */
    private ArithmeticUtil(){}

    /**
     * Return the result of tow number divide by default scale
     *
     * @param arg1
     * @param arg2
     * @return
     */
    public static double divide(double arg1, double arg2){
        return divide(arg1, arg2, DEFAULT_DIVIDE_SCALE);
    }

    /**
     * Return the result of two string number divide by scale
     *
     * @param arg1
     * @param arg2
     * @param scale
     * @return
     */
    public static double divide(double arg1, double arg2, int scale){
        return divide(Double.toString(arg1), Double.toString(arg2), scale);
    }

    /**
     * Return the result of two string number divide by default scale
     *
     * @param arg1
     * @param arg2
     * @return
     */
    public static double divide(String arg1, String arg2){
        return divide(arg1, arg2,DEFAULT_DIVIDE_SCALE);
    }

    /**
     * Return the result of two string number divide by scale
     *
     * @param arg1
     * @param arg2
     * @param scale
     * @return
     */
    public static double divide(String arg1, String arg2, int scale){
        BigDecimal var1 = new BigDecimal(arg1);
        BigDecimal var2 = new BigDecimal(arg2);
        return var1.divide(var2, scale, BigDecimal.ROUND_HALF_UP).doubleValue();
    }

    /**
     * Return the result of two number multiplicative by default scale
     *
     * @param arg1
     * @param arg2
     * @return
     */
    public static double multiply(double arg1, double arg2){
        return multiply(arg1, arg2, DEFAULT_MULTI_SCALE);
    }

    /**
     * Return the result of two number multiplicative by scale
     *
     * @param arg1
     * @param arg2
     * @return
     */
    public static double multiply(double arg1, double arg2, int scale){
        return multiply(Double.toString(arg1), Double.toString(arg2), scale);
    }

    /**
     * Return the result two string number multiplicative by default scale
     *
     * @param arg1
     * @param arg2
     * @return
     */
    public static double multiply(String arg1, String arg2){
        return multiply(arg1, arg2, DEFAULT_MULTI_SCALE);
    }

    /**
     * Return the result of two number multiplicative by scale
     *
     * @param arg1
     * @param arg2
     * @param scale
     * @return
     */
    public static double multiply(String arg1, String arg2, int scale){
        BigDecimal var1 = new BigDecimal(arg1);
        BigDecimal var2 = new BigDecimal(arg2);
        return round(var1.multiply(var2).doubleValue(), scale);
    }

    /**
     * Return the result of two number subtract by scale
     *
     * @param arg1
     * @param arg2
     * @param scale
     * @return
     */
    public static double subtract(double arg1, double arg2 ,int scale){
        return subtract(Double.toString(arg1), Double.toString(arg2), scale);
    }

    /**
     * Return the result of two number subtract by default scale
     *
     * @param arg1
     * @param arg2
     * @return
     */
    public static double subtract(double arg1, double arg2){
        return subtract(Double.toString(arg1), Double.toString(arg2), DEFAULT_SUB_SCALE);
    }
    /**
     * Return the result of two number subtract by default scale
     *
     * @param arg1
     * @param arg2
     * @return
     */
    public static double subtract(String arg1, String arg2){
        return subtract(arg1, arg2, DEFAULT_SUB_SCALE);
    }

    /**
     * Return the result of two number subtract by scale
     *
     * @param arg1
     * @param arg2
     * @param scale
     * @return
     */
    public static double subtract(String arg1, String arg2, int scale){
        BigDecimal var1 = new BigDecimal(arg1);
        BigDecimal var2 = new BigDecimal(arg2);
        return round(var1.subtract(var2).doubleValue(), scale);
    }

    /**
     * Return two number sum by the param scale value
     *
     * @param arg1
     * @param arg2
     * @param scale
     * @return
     */
    public static double add(double arg1, double arg2, int scale){
        return add(Double.toString(arg1), Double.toString(arg2), scale);
    }

    /**
     * Return two number sum by default add scale
     *
     * @param arg1
     * @param arg2
     * @return
     */
    public static double add(double arg1, double arg2){
        return add(Double.toString(arg1), Double.toString(arg2));
    }

    /**
     * Return two number sum by default add scale
     *
     * @param arg1
     * @param arg2
     * @return
     */
    public static double add(String arg1, String arg2){
        return add(arg1, arg2, DEFAULT_ADD_SCALE);
    }

    /**
     * Return two number sum by scale
     *
     * @param arg1
     * @param arg2
     * @param scale
     * @return
     */
    public static double add(String arg1, String arg2, int scale){
        BigDecimal var1 = new BigDecimal(arg1);
        BigDecimal var2 = new BigDecimal(arg2);
        return round(var1.add(var2).doubleValue(), scale);
    }

    /**
     * Return a result from arg1 by scale
     *
     * @param arg1
     * @param scale
     * @return
     */
    public static double round(double arg1, int scale){
        return round(Double.toString(arg1), scale);
    }

    /**
     * Return result by scale
     *
     * @param arg1
     * @param scale
     * @return
     */
    public static double round(String arg1, int scale){
        if (scale < 0){
            throw new IllegalArgumentException("The scale value must be an integer or zero");
        }
        BigDecimal var1 = new BigDecimal(arg1);
        BigDecimal var2 = new BigDecimal(1);
        return var1.divide(var2, scale, BigDecimal.ROUND_HALF_UP).doubleValue();
    }

    /**
     * Return a result from arg1 by default scale
     *
     * @param arg1
     * @return
     */
    public static double round(double arg1){
        return round(arg1, DEFAULT_SCALE);
    }

}